1. Field of Invention
The invention relates to ballast tamping machines such as used on railway tracks for supporting, adjusting and leveling the railway ties, and more particularly, to the tamping tools which are mounted for vertical reciprocation in such machines.
2. Description of Prior Art
In tamping machines in common use, a plurality of tamper bars are mounted for vertical reciprocation in a power-driven tamper bar support structure of the tamping machine so that the lower ends of the bars are driven downwardly into impact with the ballast mounted under and between the railway ties. In this action, the bars are also vibrated about their axes so as to impart a relatively high speed oscillatory action to the tamping tools for aiding their entry into and impacting of the ballast. Commonly, after the tools have entered a prescribed distance into the ballast, they are drawn towards each other on opposite sides of a tie, causing the ballast to move in under and to elevate the tie to a desired level of the track. The present tamper bar is designed for use with tamping machines manufactured by Tamper, West Columbia, S.C. and Plasser American Corp. of Chesapeake, Va.
As will be understood, the principal wear and deterioration of the tamping foot will occur at its lower end, where it impacts and works against the ballast. It has been heretofore proposed, see U.S. Pat. No. 3,581,664, to fit the bottom of the tamping bar with a replaceable tamper foot. During the foregoing described action, however, heavy lateral and vertical stresses are placed on the foot and its connection to the tamper bar, causing bolts to loosen with resultant premature failure of the tamper foot and bolts themselves. The use of a dovetail connection between the tamper bar and foot aids in the securing of the foot and partially relieves the stress on fastening bolts and the like. However, the driving action of the tamper feet through the ballast forces sand at high pressure between the engaged surfaces of the bar and foot, which in turn throws the load onto the fastening bolts, causing their premature fracture. Moreover, exposure of bolt heads, nuts and other fastening parts to the driving, abrasive action of the ballast quickly abrades and causes early failure of the exposed fastener parts.
Where demountable tamper feet have been secured to the lower ends of the tamping bars, it has been found necessary to weld or epoxy the bolts, against loosening and premature failure. To change the tamper foot, therefore, it has been necessary to remove the bar and foot as an entirety from the tamping machine and transport the integral bar and worn foot to a repair shop where, with the use of appropriate grinding and/or cutting machinery, the worn foot may be removed and a new foot secured in place and rewelded and shipped back to the job site. All of these operations entail a significant loss of time, since the tamping machine may be working on tracks far removed from the closest repair shop. As will also be understood, transportation from such remote track areas to repair shops is difficult, since it requires the most uneconomical stopping of a passing train or the running of a special motorized car between the job site and repair shop.
No structure has been heretofore proposed which will permit the satisfactory renewal in the field of demountable tamper feet on the tamper bars, and particularly without the removal of the tamper bars from the tamping machine.